Spark gap devices are used to generate large electrical discharges. They typically include a dielectric cylinder, which is often made of a ceramic material such as alumina, an anode on one end of the cylinder, a cathode on the other end of the cylinder and a dielectric material between the anode and cathode that electrically isolates the anode and cathode from each other. The dielectric material is typically a gas, such as argon or nitrogen, or a vacuum. When a large enough potential difference is created across the anode and cathode, the dielectric material inside the cylinder experiences dielectric breakdown and a large electrical discharge crosses the gap between the anode and the cathode.
Spark gap devices are often used in computer systems to protect circuitry from electrostatic discharge, commonly referred to as ESD. Spark gap devices are also used in lightening arrester systems to discharge lightening strikes to ground. Both types of systems apply the same concept, but lightening arrester systems operate at significantly higher potential differences and currents than ESD systems.
Spark gap devices are also used as initiators in explosives. When used for this purpose, the spark gap device includes a trigger that allows a user to actuate the spark gap device at a time of the user's choosing. The trigger is typically an electrode placed between the cathode and anode and electrically isolated from the cathode and anode. The trigger is typically driven by the secondary coil of a step-up transformer, which generates a large enough electrical field between the trigger electrode and the cathode to cause ions to begin accumulating in the gap between the cathode and the electrode. When enough ions have accumulated in the gap, migration of ions begins between the cathode and the anode and the device switches on, i.e., a short circuit occurs between the cathode and anode.
The breakdown voltage that causes the spark gap device to switch on is normally very large, e.g., thousands of volts, and the breakdown current may be thousands of amperes. In order for a spark gap device to withstand such large breakdown currents, the device is typically constructed of discrete components capable of dissipating large amounts of power. To date, it has not been feasible to embed spark gap devices in ICs because discharging a very large voltage over a very small area on an IC over a clock cycle causes a very large amount of energy to be released, which will essentially vaporize the IC.
A need exists for a spark gap device that is capable of operating at a very high voltage and that is capable of being fabricated on an IC.